Those are both excellent thoughts, Tomoe is the only connection that would make any sense and it would be kinda weird for Miles being kidnapped to be a plot point of two different books in such a short amount of time.
On the other hand that description doesn't really sound like Tomoe and the description sounds like it's trying to describe someone new. I guess we'll just have to wait and see.
Also from the looks of the Avengers cover it seems like more Mephisto stuff is coming, so whatever is being planned Miles will definitely be involved in it.